The present invention concerns new dehydrogenation agents based on derivatives of selenium and their use in the dehydrogenation in the 1,4 positions of steroids.
Derivatives of selenium are known as dehydrogenation agents. In particular, it is possible to dehydrogenate in the 1,4 position those steroids having a ketone function in the 3 position, as described by DHR Barton et al in J. Chem. Soc. Perkin I (1980), pages 2209 to 2212. In this procedure, benzene-seleninic anhydride is employed. However, this method presents two important inconveniences:
(a) This is a costly method, due to the high price of benzene-seleninic anhydride;
(b) This is a method which gives rise to secondary reactions due to the formation of selenic acid or other derivatives occurring from the reduction of the benzene-seleninic anhydride. These two inconveniences make the method difficult to utilize on an industrial scale.
While the authors disclose one example to a catalytic dehydrogenation of Lanostan-3-one using t.-butylhydroperoxide and diphenyl diselenide, the yield of the desired lanost-1-en-3-one was relatively low and the product obtained had a low melting point range, indicating contamination.
Other methods of dehydrogenation of 3-keto steroids employing aryl-seleninic anhydride are described in U.S. Pat. No. 4,220,588 to Barton et al, and Barton et al, J.C.S. Chem. Comm. (1978), pages 130-1. In addition, Meystre et al Helv. Chim. Acta 39, No. 3 pages 734-742 (1956) describes dehydrogenating .DELTA..sup.4 -3-oxo-steroids employing selenium dioxide as a dehydrogenation agent.